Toronto Metropolitan University
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Is an alibi a paper shield? An investigation of the factors that influence alibi credibility judgments

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posted on 2021-05-22, 15:00 authored by Sara Cowan
Alibis are a potentially powerful piece of evidence for innocence, but examination of criminal cases suggests that honestly offered alibis may fail to prevent wrongful convictions. Currently, little is known regarding how evaluators judge the credibility of alibis. Three studies investigated the effect of alibi moral desirability, suspect race (White/Indigenous Canadian), alibi evidence strength, and Authoritarianism on participants’ legal judgments. Participants read a fictitious police file (Experiment 1: N = 300; Experiment 2: N = 286) or newspaper article (Experiment 3: N =235) and rated a male suspect’s/defendant’s statement honesty, alibi accuracy, and the likelihood of his guilt, among other dependent measures, then completed the Authoritarianism-Conservatism-Traditionalism scale (ACT; Duckitt et al., 2010) and, in Experiment 3, the Revised Religious Life Inventory (Hills et al., 2005). In Experiments 1 and 2, participants were asked to sign a petition supporting the suspect. Results indicated that providing an alibi can be beneficial or detrimental to the suspect, depending on contextual factors and the narrative itself. In Experiments 1 and 2, alibi moral desirability affected participants’ responses, though different patterns emerged at Ryerson and at Iowa State, and moral desirability influenced judgments primarily for the Indigenous suspect. Consistent with Olson and Wells’ (2004) taxonomy, Experiment 1 showed that the strength of the physical evidence supporting an alibi is a primary determinant of judgments of its credibility. In Experiment 3, participants provided less favourable ratings for the Indigenous defendant than the White defendant, particularly when they already had more negative general feelings about Indigenous people, though this was not found in Experiment 2. More participants signed the petition when the alibi was morally desirable at Iowa State, and for the Indigenous suspect. Across all studies, higher scores on the ACT’s Authoritarianism subscale were associated with responses that were less favourable for the suspect/defendant, and many participants did not accurately define the term “alibi.” Understanding the complexities of decision-making in this context will help us better understand why some (honest) alibis are rejected, and how stereotypes and assumptions regarding the alibi provider may lead to bias in the investigation and adjudication of criminal cases.





  • Doctor of Philosophy


  • Psychology

Granting Institution

Ryerson University

LAC Thesis Type

  • Dissertation



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    Psychology (Theses)


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